When to Plant Radish in Arapahoe County, CO
Your May planting checklist for Arapahoe County, Colorado
Here's what deserves your attention in Arapahoe County, Colorado this month. Everything below is tailored to Zone 6a and timed around your local frost dates.
-
Collect radish at their peak
The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.
Looking ahead to June
- First harvests: radish
Radishes are one of the fastest-growing vegetables, with some varieties ready in under a month. They come in round, elongated, and large winter types.
Arapahoe County, Colorado is in USDA Zone 6a. The average last spring frost is May 10 and the first fall frost is October 7, giving you a growing season of approximately 150 days.
At an elevation of 7,205 feet, Arapahoe County receives approximately 21.4 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Radish during the growing season.
Arapahoe County Soil Profile
Soil Type
Loam
Soil pH
6.2-8.3
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Arapahoe County
How your county's soil matches Radish's growing requirements.
Soil pH
Your soil pH (6.2–8.3) is more alkaline than Radish prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Arapahoe County is excellent for Radish — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.5%). Annual compost additions will help Radish.
How to Plant Radish
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Radish
Sow every 2.4 weeks. Last sowing by Sep 02 to harvest before frost.
For a dedicated fall crop, sow by Jul 29.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Radish
Radish needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Radish Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.3" | 0" | ❄️ Dormant |
| Feb | — | 1.2" | 0" | ❄️ Dormant |
| Mar | — | 1.8" | 0" | ❄️ Dormant |
| Apr | — | 2.2" | 0" | ❄️ Dormant |
| May | 2.2" | 2.5" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 1.4" | 0.8" | 💧 Light watering |
| Jul | 2.2" | 2" | 0.2" | 💧 Light watering |
| Aug | 2.2" | 2.4" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 1.9" | 0.3" | 💧 Light watering |
| Oct | 2.2" | 1.7" | 0.5" | 💧 Light watering |
| Nov | — | 1.5" | 0" | ❄️ Dormant |
| Dec | — | 1.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Arapahoe County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Radish Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Radish Planting Timeline — Arapahoe County, CO
Radish Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | April 26 | Apr 26 – May 17 |
| Harvest | May 24 | May 24 – Jun 14 |
| Fall Sowing | July 29 | Jul 29 – Aug 12 |
Plant 0.5" deep · 2" apart · Rows 6" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Direct Sow |
| May | Direct Sow Harvest |
| June | Harvest |
| July | Fall Sowing |
| August | Fall Sowing |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
22–35 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 6a
📆 Growing Season
150 days in Arapahoe County
Growing Tips for Radish in Arapahoe County
Direct sow Radish outdoors after May 10 in Arapahoe County when soil has warmed and frost danger has passed.
Your generous 150.0-day season in Arapahoe County allows multiple plantings of Radish. Sow every 11.0 days for continuous harvest.
Common pests for Radish in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Direct sow every 1-2 weeks for continuous harvest. Do not transplant. Harvest spring radishes promptly to prevent them from becoming pithy and hot.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Radish in Other Locations
Frequently Asked Questions
When should I plant Radish in Arapahoe County, CO?
Arapahoe County is in Zone 6a with an average last frost of May 10. Plan your Radish planting based on this frost date — see the calendar above for exact timing.
What planting zone is Arapahoe County, CO?
Arapahoe County, Colorado is in USDA Hardiness Zone 6a. The average last spring frost is May 10 and first fall frost is October 7.
Your Arapahoe County Garden Planner — Free
A 24-page printable planner built for Arapahoe County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.